Preheat oven to 375°F (190°C) and grease a 9x13-inch baking dish with butter or oil.

Wash and dry zucchini, slice into ¼-inch thick rounds.

Sprinkle zucchini lightly with salt and let sit 10 minutes to draw out excess moisture.

Pat zucchini dry with a paper towel.

In a large bowl, mix sour cream (or yogurt), half of the cheese, garlic powder, chopped dill, salt, and pepper.

Stir in zucchini and chopped onion until evenly coated.

Pour zucchini mixture into the prepared baking dish and spread evenly.

Sprinkle remaining cheese on top.

Mix breadcrumbs with melted butter and sprinkle over the cheese layer.

Bake uncovered for 30–35 minutes until bubbly and golden on top.

Optional: broil for 2–3 minutes at the end for extra crispiness, watching carefully.

Let casserole rest for a few minutes before serving to set the layers.